RCP Concentration Calculations and Data
Final Version, background data, acknowledgements and further info.

Summary

The Task Group 'RCP Concentrations Calculation and Data' harmonised and consolidated greenhouse gas concentration and emission datasets for the pre-industrial control runs, 20th century, and the Representative Concentration Pathways (RCPs). The mixing ratios for the long-lived greenhouse gases provided below are the CMIP5 recommendation for Earth System Models in preparation of the IPCC Fifth Assessment Report. On this website: we provide as well additional background data, which is NOT part of the CMIP5 recommendations. For more information, please see the central CMIP5 PCMDI website and the RCP emission scenario database and our documentation: M. Meinshausen, S. Smith, et al. "The RCP Greenhouse Gas Concentrations and their extension from 1765 to 2500" (2011), Climatic Change (Special Issue on RCPs) (PDF) (HTML)

Data download

On this website, only a part of the recommended RCP CMIP5 datasets are available, i.e. the GHG concentration timeseries (which are as well mirrored the central RCP emission scenario database ). For transparency purposes, this website here documents all consolidated GHG concentration, harmonized emission datasets and forcing timeseris that have been used within the RCP 'concentration calculation and data' group. Please note again, that only the GHG concentrations shown below are CMIP5 recommendations, with forcing agents like tropospheric ozone, stratospheric ozone, aerosol abundances, and land-use pattern information to be taken from elsewhere, as detailed on the central CMIP5 PCMDI website and the RCP emission scenario database pages. The data can be used free of charge and for non-commercial purposes. Please cite: M. Meinshausen, S. Smith et al. "The RCP greenhouse gas concentrations and their extension from 1765 to 2500" (2011), Climate Change, Special RCP Issue.(PDF) (HTML)

Further Information

The Task Group 'RCP Concentrations Calculation and Data' was asked to produce harmonised and consolidated concentration and emission datasets for the four RCP datasets RCP3-PD (low), RCP45 (medium-low), RCP6 (medium-high), and RCP85 (high).

A set of 20th century global and annual mean mixing ratios was compiled based on available authoratative sources. The greenhouse gas mixing ratios, in particular CO2, N2O, HFCs, PFCs, SF6 and the ozone depleting substances ODS, are recommended for being used in the 20th century runs in preparation of IPCC AR5. Here, data is provided for the full time span from 1765 to 2005, although modelling groups might decide to start their model runs only in 1850. Please consult the CMIP5 PCMDI website for further information in regard to other compounds, including short-lived greenhouse gas concentration fields for tropospheric ozone or methane. These additional short-lived compounds are included in the above consolidated datasets but are not the CMIP5 recommendation. More information ...

We harmonised greenhouse gas, tropospheric ozone precursor and aerosol emissions across the five RCP regions OECD, REF (Economies in Transition), ASIA, MAF (Middle East and Africa), and LAM (Latin America). Due to this harmonisation process, all harmonised RCPs now share the same 2000 to 2005 emission data. The harmonised 2000-2005 data is based on, where available, RCP year 2000 inventory data, inverse emission estimates (mainly for HFCs, PFCs, SF6), or literature sources (e.g. using Marland et al. for fossil&industrial CO2 emissions). The post-2005 were adjusted gas-by-gas using linearly decreasing scaling factors or offsets. (For background information and all the original RCP emissions, please visit the RCP emission scenario database. In the future, harmonised emissions will be available as well from there.)

The RCP emission scenarios produced by the integrated assessment models extend only to 2100. In order to provide data needed for conducting long-term climate change projections the concentration values from these scenarios have been extended to 2300 (The data provided here actually extends all the way to 2500). These extensions, the so-called ECPs (Extended Concentration Pathways), were calculated using simple rules developed in a series of stakeholder consultations. These do not represent fully consistent scenarios. The rules used for the extension are:

• RCP3PD: Constant emissions after 2100.
• RCP4.5: Constant concentrations after 2150 with smooth transition between 2100 and 2150.
• RCP6.0: Constant concentrations after 2150 with smooth transition between 2100 and 2150.
• RCP8.5: Constant emissions after 2100 and constant concentrations after 2250 with smooth transition of emissions between 2150 and 2250.

Apart from the standard extensions for each RCP, two supplementary extensions are provided above. In particular, stakeholders were interested in an extension which combines concentrations again in the long-term, after initially following different pathways. Thus, we provide two supplementary extensions, which are not part of the CMIP5 recommendations:

• SCP6-TO-4.5: Starting from RCP6, concentrations are adjusted after 2100 in order to join the levels of the next lower scenario RCP4.5 by 2250.
• SCP4.5-TO-3PD: Starting from RCP4.5, concentrations are adjusted after 2100 in order to join the levels of the next lower scenario RCP3PD by 2250.

The RCP emission scenarios were ammended by a series of emissions that were not provided by the Integrated Assessment Models. For example, most of the emission projections for ozone depleting substances are generously provided by the WMO assessment report researchers Guus Velders, John Daniel et al. (WMO 2006). Only slight modifications have been done from the WMO 2006 A1 baseline scenario. Namely, HCFC 142b emissions have been ajusted over 2005 to 2007 towards the inverse emission estimates reported in Montzka et al. (2009). RCP3-PD provided alternative pathways for some ODS, which replaced respective WMO A1 baseline projections.

The harmonised RCP emission datasets were then run through a reduced-complexity coupled carbon cycle climate model, namely MAGICC 6.3. In reality, there is some uncertainty on what the mixing ratios are going to be for a particular emission pathway. In particular for CO2, where carbon cycle feedback uncertainties suggest a relatively broad range in possible future concentrations, a decision needed to be made what the consolidated concentration recommendation for CMIP5 should be. Here, both the climate and carbon cycle components are calibrated to provide a medium-range estimate of models available in IPCC Fourth Assessment Report. Namely, the carbon cycle model has been calibrated towards the median of C4MIP (Friedlingstein et al., 2006) model comparison results and the climate model component reflects the median of calibrations to CMIP3 AOGCMs (Meehl et al., 200X). The calibrations towards the individual models are decribed in Meinshausen et al.(2011, ACP).

For information purposes only, we provide here the radiative forcing results (following a standard IPCC forcing definition, i.e. after stratospheric temperature adjustment). These forcings will as much as possible be diagnosed from the radiative transfer schemes of ESMs and not be used as input. However, for some models of intermediate complexity that do not have all gas cycles included, these standardised radiative forcing estimates might be useful for running RCPs. All radiative forcing time series closely reflect either best-estimate IPCC AR4 values for 2005, or, if not available, radiative efficiencies, e.g. for individual HFC and ODS gases.

Regarding volcanic forcing: Note that volcanic forcing, as the other radiative forcing series, are here provided only for transparency, not as a CMIP5 recommendation. The radiative forcing series was derived from the GISS radiative forcing series by Sato et al., available on data.giss.nasa.gov and extended by the zonal radiative forcing estimates by Hegerl, Crowley et al. 2006, as provided on the Nature Supplementary Information website . Radiative forcing was multipled by 0.7 and shifted for a zero historical mean.

Citation

Contact

Malte Meinshausen (malte.meinshausen +add+ pik-potsdam.de)
Steve Smith (ssmith +add+ pnl.gov)
RCP3-PD (IMAGE): Detlef van Vuuren (detlef.vanvuuren +add+ pbl.nl)
RCP4.5 (MiniCAM): Allison Thomson (Allison.Thomson +add+ pnl.gov)
RCP6 (AIM): Toshihiko Masui (masui +add+ nies.go.jp)
RCP8.5 (MESSAGE): Keywan Riahi (riahi +add+ iiasa.ac.at)

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